The invention relates to the manufacture of a thermally insulated container for the storage or transport of liquefied gases, for example propane, methane or natural gas, comprising a lining of polyurethane foam arranged on the inner surface of a rigid outer shell. Containers of this kind are described, for example, in applicant's British Pat. No. 1,173,424.
In the manufacture of such thermally insulated containers, the lining of polyurethane foam is applied to the rigid outer shell by spraying a number of layers of polyurethane foam on top of each other until the lining has reached the desired thickness. The polyurethane foam is preferably applied mechanically by means of specifically designed spraying apparatus, such as described, for example, in applicant's British Pat. No. 1,300,352.
Sometimes it is necessary to carry out the spraying of polyurethane foam by a spraying apparatus which is operated manually, for example, at the corners of a prismatic tank, or for carrying out repairs to the polyurethane foam lining of an existing container. In such cases, some of the foam already applied has to be removed by cutting or grinding beforehand. However, after having cut or ground the polyurethane foam lining, it is not possible to obtain a good bond to a further layer of polyurethane foam (i.e., the bond strength is less than the cohesive strength of the foam).